Automatic firearm with breech mechanism unlocked by the recoiling barrel



B. MAILLARD April 8, 1969 Sheet AUTOMATIC FIREARM WITH BREECH MECHANISM UNLOCKED BY THE RECOILING BARREL Filed April 1, 1968 @m ma Sheet B. MAILLARD BY THE RECOILING BARREL AUTOMATIC FIREARM WITH BREECH MECHANISM UNLOCKED April 8, 1969 Filed April Apnl 8, 1969 'B. MAILLARD 3,437,006

AUTOMATIC FIREARM WITH BREECH MECHANISM UNLOCKED BY THE RECOILING BARREL Filed April 1, 1968 Sheet 4 of 4 3,437,006 AUTOMATIC FIREARM WITH BREEUH MECHA- NISM UNLOCKED BY THE RECOILING BARREL Bernard Maillard, Geneva, Switzerland, assignor to Brevets Aero-Mecaniques S.A., Geneva, Switzerland, a society of Switzerland Filed Apr. 1, 1968, Ser. No. 717,841 Claims priority, application Luxembourg, Oct. 6, 1967, 54,608 Int. Cl. F4111 /04 US. Cl. 89-169 9 Claims ABSTRACT OF THE DISCLOSURE nited States Patent 0 with the recoiling part during which the first piston will operate the second piston, which in turn unlocks the breech mechanism.

The present invention relates to automatic or semiautomatic fire-arms of the type in which the breech mechanism is arranged to be unlocked by a member connected to a recoiling part of the fire-arm. The invention is more particularly, but not exclusively, concerned with fire-arms whose breech mechanism is locked and unlocked by rotation about an axis parallel to the axis of the barrel of the fire-arm.

An object of the present invention is to provide firearms which fulfill the various practical considerations, in particular in that their rate of fire can easily be adjusted.

According to the present invention, a fire-arm of the type in question is arranged so that a primary cylinder, in which is disposed a primary piston connected mechanically to the above mentioned recoiling part, is made to communicate with a secondary cylinder in which is disposed a secondary piston forming or actuating the above mentioned member for controlling the unlocking, said cylinders being filled with liquid between the two pistons and being rigid with a non-recoiling part of the fire-arm; the primary piston is given an active cross-section greater than that of the secondary piston so as to increase the speed imposed on the secondary pisto by the displacement of the liquid, with respect to the speed of recoil of the recoiling part; at least one communication passage is provided between the two sides of the head of the primary piston, said communication passage being adapted to be blocked off at an adjustable point of the stroke of the primary piston, said adjustable point being the point from which the secondary piston is driven back; due to which, since the breech mechanism is unlocked with a shorter or longer delay after the beginning of the recoil, the rate of fire is higher or lower.

Various other features of the invention will become apparent from the following specific description of a preferred embodiment of the invention, given, merely by way of example, with reference to the accompanying drawings in which:

FIGURE 1 shows an automatic fire-arm arranged according to the invention, partly in axial section and partly in a view from the exterior;

FIGURE 2 (divided by a vertical dot-dash line into two parts 2a and 2b intended to be considered end to end) shows in axial section, on an enlarged scale, the elements at the bottom of FIGURE 1;

FIGURE 3 shows in perspective the head of the primary piston visible in axial section in FIGURE 2a;

FIGURES 4 and 5 show the unit formed by the primary piston and its cylinder, respectively in transverse section (the piston, which is not in section, being seen from the left of FIGURE 2a) and in a view developed in the plane of the drawing;

And FIGURE '6 illustrates the operation of the fire-arm with the aid of a curve.

The embodiment shown in the drawings is a heavy machine gun of calibre comprised between 20 and 50 mm.

With regard to the fire-arm as a whole, it is arranged so that its breach mechanism 1 can be unlocked at each shot by a member connected to the recoiling part of the firearm. Preferably, the breach mechanism is of the type that is locked and unlocked by rotation about an axis parallel to the axis of the barrel of the fire-arm.

In the following, it wvill be supposed that the fire-arm, with the exception of its mechanims for unlocking the breech mechanism, conforms to the indications given in the US. patent application Serial No. 717,524 filed April 1, 1968, by the present applicant for Semi-Automatic or Automatic Fire-Arms, and that the breech mechanism in itself conforms to the indications given in US. patent application Ser. No. 622,643 filed on March 13, 1967, by the present applicant for Improvements in Automatic and Semi-Automatic Guns Having a Double Feed Mechanism.

In such a fire-arm, the breech mechanism 1 comprises a breechblock 2 including, on the one hand, at its front part, a cup-shaped recess 3 with which the rear end (not shown) of the cartridges to be fired comes into engagement, and on the other hand, exteriorly, locking lugs 4 which co-operate with lugs 5 formed on a sleeve 6, which receives the barrel 7 in a removable manner due to a bayonet type joint 8. In addition, the breech mechanism 1 comprises a casing 9 formed of two halves separated approximately by the plane of FIGURE 1, which can slide without rotation in a fixed breechcase 10 and which is disposed around the breechblock 2. A spindle 11 passes through this breechblock and is connected, at the interior of the breechblock, to a firing pin 12, and at the exterior of the breechblock, to the casing 9. The lugs 4 of the breechblock 2 are situated on the same cylinder of revolution as a part at least of the surface of the casing 9, which permits the breechblock 2 to be guided by contact of the casing 9 and of at least certain of its lugs 4 with guiding surfaces 13 formed, at the level of openings 14 for the introduction of the cartridges, on the large sides 15 of a part of the breechcase 10 whose cross-section is substantially rectangular, the small sides being designated by 16. In front of its part 15, 16, the breechcase 10 comprises .a part 17- whose interior cross-section and exterior cross-section are cylindrical.

A spring 18, acting on the firing pin 12, tends to drive the unit formed by the firing pin and the casing 9 towards the front of the breechblock 2. In order to transform into a rotary movement of the breechblock the translatory movement which is produced between the casing 9 and the breechblock 2 when the breechblock arrives substantially at the closing position illustrated in FIGURE 1, the spindle 11 carries two rollers (not shown) co-operating respectively with skews 19 formed in a cylindrical enlarged portion 20 of the breechblock 2.

At its exterior surface, the casing 9 carries two longitudinal projections such as 21, Whose longitudinal lateral faces (not shown) co-operate with the interior faces of the large sides 15 of the breechcase 10 to prevent it from rotating at the interior of this breechcase. The lower longitudinal projection 21 comprises a front face 21a adapted to co-operate with the projection 22 of an unlocking pushpiece 23 which will be more explicitly described hereafter and which is provided for unlocking the breech mechanism 1 with respect to the sleeve 6.

In order to maintain the casing 9 imperatively in its extreme rear position with respect to the breechblock 2 during the reciprocating movement of the breech mechanism 1 at the interior of the breechcase 10, a leaf-spring 24, carried by the brechblock 2, tends to project by its rear part against a bearing face 25 of the casing 9, whereas an inclined surface 26, carried by the breechcase 10, can retract the leaf-spring 24 by acting on a push-piece 27 passing through the casing 9.

The sleeve 6 comprises esentially, together with the barrel 7, the recoiling part of the fire-arm whose breechcase is fixed. The sleeve 6 can be guided with respect to the breechcase 10, on the one hand at the front, by contact of a collar 28 with the interior surface of a nut 29 screwed in the cylindrical part 17 of the breechcase, and on the other hand at the rear, by contact with the interior surface of a ring 30 which is maintained, in the manner indicated later on, against a shoulder 31 of the part 17.

It is known that the operation of such a fire-arm is the following. When a cartridge is placed in the chamber 32 which is limited towards the rear in the barrel 7 by the cup-shaped recess 3, the cartridge is fired, which causes the recoil of the unit formed by the barrel 7, the sleeve 6 and the breech mechanism 1. The push-piece 23 is driven towards the rear, in the manner described hereafter, and drives, by its projection 22, the casing 9 in an accelerated movement. The casing 9, while recoiling, rotates in the breechblock 2 so that it can free itself from the sleeve 6. The residual pressure of the gases in the chamber 32 contributes to make the breech mechanism 1 recoil, which it does while compressing a counter-recoil spring, a portion of which is shown at the right hand end of FIGURE 1. The breech mechanism 1 abuts at the end of its stroke against a damping device provided with springs. During the recoil, the empty cartridge is ejected.

The breech mechanism is then returned towards the front by the damping device and the counter-recoil spring. The breech mechanism drives the cartridge which was located in position for introduction, and introduces this cartridge into the chamber 32. The casing 9, which had been maintained at the rear of the breechblock 2 by the leaf-spring 24 during the reciprocation of the breech mechanism, is freed by the action of the inclined surface 26, and the spring 18 drives the casing 9 towards the front, which locks the breechblock 2 by making it rotate, and then brings the point of the firing pin 12 into the cup-shaped recess 3 (new shot).

This being the case, in order to displace the pushpiece 23 towards the rear during the recoil of the sleeve 6 and the barrel 7, a primary cylinder 33, in which is disposed a primary piston 34 mechanically connected to the sleeve 6, is made to communicate with a secondary cylinder 35, in which is disposed a secondary piston (or plunger) 36, these cylinders 33 and 35 being filled with liquid between the two pistons 34 and 36 and being rigid with the breechcase 10; the primary piston 34 is given a larger active cross-section than that of the secondary piston 36 so as to increase the speed that the liquid driven by the primary piston imposes on the secondary piston, with respect to the speed of recoil of the sleeve 6; and at least one passage of communication is provided between the two sides of the head 34a of the primary piston 34, this passage of communication being adapted to be blocked off at an adjustable point of the stroke of the primary piston 34.

Advantageously, the two cylinders 33 and 35 are formed in the same tubular piece 37 oriented parallel to the firing axis and placed in the annular space left free between the sleeve 6 and the cylindrical part 17 of the breechcase 10. The tubular piece 37 can be fixed between the nut 29 and the ring 30 in a manner such that it can maintain the ring 30 against the shoulder 31. The piece 37 is engaged in the ring 30 and/or in a collar of the sleeve 6 situated to the rear of the collar 28 by bearing surfaces of cross-sections other than circular so that its orientation with respect to the fire-arm remains unchangeable. This permits the common axis of the cylinder 35 and a piston 36 to be situated nearer to the breech mechanism 1 than the common axis of the cylinder 33 and the piston 34, by reason of the difference of the cross-sections of these cylinders. If the push-piece 23 is then aligned with the piston 36, it will be noted that the overhang with which the projection 22 of the push-piece 23 acts on the projection 21 of the casing 9 is decreased.

The piston 36 can be arranged in the form of a plunger, that is to say in the form of a rod of constant diameter adapted to penetrate into the chamber 38 which is formed in the tubular piece 37 betwen the cylinders 33 and 35 This r-od advantageously has a cavity 39 opening into the chamber 38 and blocked ofi? by a bottom 40 at the end near to the push-piece 23 due to which, on the one hand, the quantity of liquid is increased (decrease of the maximum temperatures by distribution of the calories in a greater volume), and on the other hand, the pressures generated at the interior of the rod can dilate the rod (improvement of the fluid-tightness). The push-piece 23 is itself mounted in a tubular guide 41 which is aligned with the cylinder 35 and which bears at the front against the ring 30, this guide comprising a slot 42 for the passage of the projection 22 and housing a spring 43 adapted to return the push-piece 23 and the piston 36 into firing position.

In order to be able to regulate the point of the stroke of the primary piston 34 for which the communication passage between the two sides of the head 34a of this piston is blocked off, this passage is advantageously formed by grooves (or channels) hollowed out in the interior wall of the tubular element 37, the form and the disposition of these grooves and of the head 34a being such that, according to the angular position imposed to this head, the head itself blocks off these grooves for a variable longitudinal position at the interior of the cylinder 33. Moreover, preferably another communication passage is opened after the piston has travelled a constant distance from the block off point, whatever be the longitudinal position of this point.

For this purpose, as shown in detail in FIGURES 3 to 5, at least one (two in the example illustrated) group of two grooves 44 and 45 is formed in the part of the tubular piece 37 forming the primary cylinder 33. These grooves 44 and 45 are parallel to the axis of the cylinder 33 and end by helical sides 44a and 45a of equal pitch (that is to say, if the cylinder is developed onto a plane as shown in FIGURE 5, the developed sides 44a and 45a are rectilinear and inclined preferably with the same slope). Furthermore, the piston head 34a rests on the part of the cylinder 33 left intact between the grooves 44 and 45, by bands 46 limited by helical sides 46a and 46b having preferably the same pitch as the sides 44a and 45a (that is to say, developing along segments parallel to the developments of these latter sides, as shown in FIGURE 5). Finally, means are provided permitting the adjustment of the angular position of the head 34a with respect to the piece 37.

In the longitudinal position shown in FIGURE 5 for the piston head 34a, whose rear face 47 has been indicated by a broken line, it can be seen that the grooves 44 communicate freely with the two sides of the piston head. As soon as the piston head has advanced through the distance a, the bands 46 begin to prevent the communication between these two sides, until the head has travelled again a distance equal to the distance b (measured axially) which separates two successive grooves 44 and 45, increased by the width (measured axially) of the bands 46. At this time, it is the grooves 45 that reestablish the communication. It can be understood that, if the piston head is rotated about itself, which corresponds to a vertical displacement of its development in the plane of FIGURE 5, the distance a, which is indicated in this figure for its minimum value, will increase, whereas the distance b+c remains constant. In other words, it is for a different axial position of the piston 34 that the communication between the two sides of the piston head begins to be cut off and that, consequently, the delivery of the liquid which causes the displacement of the secondary piston 36 begins to be produced, Whereas the useful delivery stroke b+c of the primary piston 34 and, consequently, the stroke imposed on the secondary piston 36 remain constant.

As shown in FIGURE 4, it is appropriate to give the tubular piece 37 an exterior cross-section approximately square, which facilitates its housing between the sleeve 6 and the part 17 of the breechcase 10, and to form the grooves 44 and 45 at the level of certain of the angles of the piece 37, which permits this piece to resist better the high pressures which are cyclically generated in these grooves.

In order that the piston head 34a can be driven by the sleeve 6 during its recoil while permitting the gunner to adjust its angular position, the head is fixed on a rod 34!) which passes through the bottom of the cylinder 33, through packings 48, in a manner to hook onto the collar 28 and to be able to carry a lever 49 on which the gunner can act.

In order to facilitate the assembling and dismantling of the fire-arm, the rod 34b can butt by a shoulder 50 against the rear face of the collar'28, which can thus drive the rod 34b towards the rear. The rod 34b passes through the collar 28 within a sleeve 51 to which the rod 34b is connected in rotation by a direct-drive dog-clutch system 52. This sleeve 51 carries the lever 49 and a shoulder 53 which butts against the front face of the collar 28. Since the sleeve 51 is fixed to the rod 34b (in a dismantlable manner), it will be understood that the collar 28 can drive the rod 34b towards the front due to its contact with the shoulder 53.

In order to facilitate the return, to the rear (towards the right of FIGURE 2a) of the piston head 34a, of the liquid that had been admitted in front (towards the left) of this head during the recoil of the sleeve 6, it is appropriate to provide this head with a one-Way valve. Advantageously, as shown in FIGURE 2a, this valve is formed by the head itself by mounting it in a slidable manner on the rod 34b and by making channels 54 pass through this head, these channels 54 being adapted to be blocked oil? by a disc 55 fixed with respect to the rod 3412.

For this purpose, the rod 34b can be provided with an extension 340 of cross-section other than circular, and in particular square, on which is fitted a hole 56, of corresponding cross-section, formed in the head 34a. Abutments, formed for example by a ring 57 and by the disc 55, are provided on the extension 34c for ending the stroke of the head 34a.

As a result, a fire-arm is provided in which the pushpiece 23 is displaced in the following manner, for effecting the unlocking of the breech mechanism in the manner indicated above.

When the sleeve 6 recoils with the barrel 7, the collar 28 drives the rod 34b towards the rear along a distance equal to the recoil of the sleeve 6. From the beginning of the movement towards the rear of the rod 34b, the piston head 34a is applied against the disc 55, which blocks oif its channels 54.

After having travelled the distance a (FIGURE the head 34a passes the sides 44a of the grooves 44 and is thus rendered fluidtight. From this moment and until the supplementary stroke b+c has been travelled, the head 34a delivers the liquid, which displaces the secondary p ston 36 along a distance equal to the product of the distance b+c times the ratio of the cross-sections between the primary piston 34 and the secondary piston 36. If for example this ratio is equal to 3, it can be seen that the secondary piston 36 is driven along a distance equal to 3(b-l-c). During its recoil, the piston 36 drives the push-piece 23 against the action of the spring 43, which determines the unlocking of the breech mechanism, then its driving towards the rear in the manner described above.

When the sleeve 6 comes back towards the front, it drives directly the rod 3412 then the head 34a, once this head has been stopped by the ring 57. The liquid which was delivered beforehand to the front of the head 34a, by passing along the bands 46 by the intermediary of the grooves 44, can then come back to the rear of the head 34a by passing through the channels 54.

It should be noted that when the two sides of the head 34a are put in communication by the grooves 44 or 45, the rod 34!) acts again as a piston and can thus cause the displacement of the secondary piston 36, but with the speed which is then only proportional to the ratio of the cross-sections of the rod 34b and the piston 36.

FIGURE 5 shows the position of the head 34a for which the distance a to be travelled by this head before the recoil of the secondary piston 36 begins is minimum. This means that the rate of fire is maximum. To decrease this rate, the gunner acts on the lever 49 in a manner to make the read 34a turn in the direction which corresponds to a lowering of its development in FIGURE 5. This increases the distance a and produces a decrease in the firing rate, due, in the first place, to the fact that the delay between the beginning of the recoil of the sleeve 6 and the beginning of the recoil of the secondary piston 36 is increased. Another phenomenon comes into play to decrease this firing rate, as is shown in FIGURE 6. This figure shows, as a function of the time t on the abscissa, the variations of the distance d of any point of the sleeve 6, measured parallel to the firing axis, with respect to the reference system formed by the breechcase 10. FIGURE 6 shows that the distance travelled per unit time by the sleeve 6 during the recoil, in the zone of operation corresponding to the unlocking of the breech mechanism, decreases as a function of time. This means that, in order to travel the constant distance b+c neces sarry for the unlocking of the breech mechanism, the sleeve 6 needs a shorter time 1 when this locking takes place with the minimum of time after the beginning of the recoil (distance a minimum) than the time t taken when the operation of unlocking begins with a certain delay from the beginning of the recoil (distance a greater than its minimum value). Consequently, the rate of fire decreases under the triple effect of the delay imposed on the beginning of the operation of unlocking, the increase of the time necessary for travelling the unlocking distance [2+0 and the proportional lowering of the residual pressure.

By modifying the angular position of the piston head 34a, the rate of fire can thus be varied within wide limits. The manufacturer can thus adjust the fire-arms of a determined type according to the application envisaged with the object of obtaining a maximum effectiveness as a function, for example, of the elasticity of the support for the fire-arm.

The most favourable firing rate can also be determined by the gunner, for example in case of ground-ground firing or firing against aircraft.

Although the present invention has been described with reference to a particular embodiment, it should be understood that the invention is not limited thereto, and that various modifications are possible Without departing from the spirit or scope of this invention.

What I claim is:

1. For a fire-arm of the type in which a breech mechanism is arranged to be unlocked by a member operatively connected to a recoiling part of the fire-arm, means for controlling the point during recoiling at which the said member causes unlocking of the breech mechanism comprising: a first piston disposed in a first cylinder and connected mechanically to said recoiling part, and a second piston having an active cross-section smaller than that of the first piston and disposed in a second cylinder and positioned to be operated to unlock said breech mechanism, said cylinders being filled with a body of liquid between the two pistons so that movement of the said body of liquid by the first piston causes movement of the second piston for unlocking said breech mechanism, and at least the first of the two cylinders being rigid with a non-recoiling part of the fire-arm, the first piston having an adjusting means associated therewith for selecting the portions of the travel of the first piston with the recoiling part of the fire-arm during which the first piston will move the body of liquid to move the second piston to unlock the breech mechanism.

2. A fire-arm according to claim 1 wherein the said adjusting means includes at least one communication passage between the two sides of the first piston arranged such that when the passage is open and the first piston moves toward the second piston, liquid from said body of liquid will pass through the passage to the opposite side of the first piston, and when the passage is closed and when the first piston is further moved toward the second piston, the body of liquid, being trapped between the first and second pistons, moves the second piston to unlock the breech mechanism, and including means for selectively opening and closing said communication passage during the travel of the first piston with the recoiling part.

3. A fire-arm according to claim 2 wherein said at least one passage comprises at least one groove formed in the wall of the first cylinder, the lateral surface of the first piston between the two said sides being shaped to selectively block-off the said groove, the said first piston being adapted to be rotated about its own axis, and wherein the angular position of the first piston about its own axis determines the point during the said travel of the first piston at which its lateral surface blocks-01f the groove, thereby closing the passage.

4. A fire-arm according to claim 2 including at least a pair of communication passages arranged such that during the travel of the first piston with the recoiling part of the fire-arm, one of said passages is closed after which the other of said passages is opened.

5. A fire-arm according to claim 2 wherein said adjusting means includes at least one pair of passages, each passage of the pair including a groove formed in the wall of the first cylinder, the two grooves being spaced from each other in a direction parallel to the axis of the first cylinder so that during the travel of the first piston one of said grooves is blocked-off before the other is opened, the lateral surface of the first piston being shaped to selectively open or block-0T1 each of said grooves, the first piston being adapted to be rotated about its axis such that the angular position of the first piston about its axis determines the point during said travel of the first piston at which the lateral surface opens or blocks-oil the said grooves, the space between the said grooves being shaped such that the distance traveled by the first piston between the point of block-oil of the first groove and the opening of the other groove of the pair is constant regardless of the angular position of the first piston.

6. A fire-arm according to claim 5 wherein the space between the said pair of grooves is in the form of a land having substantially parallel, helical sides, and the said lateral surface of the first piston includes a raised band having substantially parallel, helical sides, the pitch of the two said helical sides being substantially equal to each other, and the said band of the first piston resting on the said land of the first cylinder.

7. A fire-arm according to claim 2 wherein the first piston includes a one-way valve permitting the rapid flow of liquid from the said opposite side of the first piston to the said body of liquid between the two pistons as the first piston moves away from the second piston during the return to the firing position of the fire-arm.

8. A fire-arm according to claim 1 wherein the first and second cylinders are formed in a single integral piece disposed substantially parallel to the axis of fire of the fire-arm, the axis of the second cylinder being closer to said axis of fire than the axis of the first cylinder.

9. A fire-arm according to claim 8 wherein the said integral piece forming the first and second cylinders has an exterior cross-section of an approximately square shape, the said passage being formed in a plane passing through the axis of the integral piece and also through one of the corners of the said square.

References Cited UNITED STATES PATENTS 3,058,398 10/1962 Barr 89-169 BENJAMIN A. BORCHELT, Primary Examiner.

STEPHEN C. BENTLEY, Assistant Examiner. 

